Turntable driven recording mechanism



July 1., 1941'. M E OL-UNS 2,247,747

TURNTABLE DRIVEN RECORDING MEGHAISM Filed oct. 51, 1939 Patented July 1,1941

UNITED STATE TURNTABLE Dalvaglzcoanma MECHA- Milford E. Collins, Los Angeles, Calif., assigner to Radio Corporation of America, al corporation of Delaware Application october' s1, 1939, serial No. 302,175

1 o` calms. K (cmi-.411)

This invention relates to sound recording apparatus and particularly to a disc record cutter driving mechanism.

In the art of wax` and acetate sound recording, one of the preferred methods of progressively shifting the cutter radially across `the wax or acetate disc is by a lead screw rotated from the turntable spindle or the turntable itself. One end of the lead screw is usually attached adjacent therim of the turntable in a manner such that the other end of the lead screw may b e swung over the spindle for connection thereto or swung to one side for the removal of the record. 'I'his particular type of mechanism is Apreferable for instantaneoussound recorders utilizing acetate discs for immediate reproduction. 'I'he cutter head for acetate discs imposes upon the lead screw and prime mover considerable load, since the material being cut is of a heavier composition than the usual recording wax. Furthermore, as the axis of the lead screw is in a plane parallel to the plane of they turntable, the connection between the lead screw and the turntable or spindle is made through a countershaft geared to the lead screw at one end and positively connected to the other end of the turntable spindle or frictionally connected to the record disc on the turntable which supports the lead screw assembly. It has been found preferable to positively drive the lead screw so that a den'ite angular relationbetween the turntable rotations and the rotations of the lead screw. In such a connection, however, it is diilicult, in commercial manufacture, to make the flat-sided or square-shank of the spindie and the accommodating aperture so perfect that there will be no irregularities in the. connection therebetween `for the different angular positions at which connection may be made. It is also difficult, in commercial manufacture, to prevent slight eccentricities occurring in the rotation of the turntable and spindle. Such discrepancies and eccentricities generally produce a periodicbinding action between the driven shaft and spindle such as to similarly vary the load on a prime mover. Because of the flexibility of the mechanical lter, these variations inloadv introduce what are commonly called fwowsf or a once-or-twice-.around distortion in the, cut record. This, of course, is detrimental to good recording. The present invention is thus directed .to a simple and eilicient connecting unit for pre-- venting variations in load or other irregularities in the' connecting mechanism from affecting the recording.

The principal is to improve sound-on-disc recording.

A further object of the invention is to provide a -connection between a driving and a driven element connectable in several diil'erent angular re- .'lationships which will be uniform at all times reship exists at all times between the revolutions of the record on the turntable and the lead screw. This producesa more uniform pitch and width to the grooves being cut. Also, to maintain the proper frequency of the produced sounds, it is desirable that the turntable and record blank rotate at a constant speed.. To aid in obtaining this constant speed, mechanical lters and flywheels are provided between the prime mover and the turntable. However, variations in load on the cutter, caused by a binding action at any point in the mechanism will 'tend to create variations in turntable speed.

In this type of sound recorder, provisionl must l be made for the eady connection of the turntable y spindle with the lead screw so that the record gardless of discrepancies in the different angular connection relationships.

A further object of the invention is to provide a positive connection between a turntable spindie and a disc cutter lead screw which will equalize the load on the prime mover for diiIerent anguiar connections between the spindle and lead screw.

A further object of the invention is to provide 4 a spindle driven cutter lead screw vconnecting cutter may be quickly placed in position 'for operation and quickly removed afterthe record is cut. In the present invention, this isaccomplishedby 'providing a fiat-sided or squareshanked spindle and the shaft connecting the lead screw with the flat-sided spindle, with a socket containing a resiliently mounted broached member which 'accommodates the shank" of the spindle. There is thus provided a. constant lratio mechanism which will compensate for minor irregularities at one point and for greater irregularities at a second point. i i

Although the novel features which are believed to'be characteristic of this invention will be pointed out with particularity in the claims appended` herewith; the invention itself. its objects and advantages, the manner of its organization and the mode of its operation'will be better under- 'stood` by referring to the following description read in conjunction with the accompanying drawing forming a part thereof, in which Figure 1 is a front elevational view of a soundon``disc recorderv embodying the invention; A Figure 2 is across-sectional view of the conobiect of the invention, therefore,

necting mechanism between the turntable spindle and the lead screw assembly taken along the line 2--2 of Fig. 1;

Figure 3 is a detailed sectional view of the confrom a prime mover such as a motor Iii through` a reduction gear box il, a mechanical lter I2, a

shaft i3 and a coupler it. A flywheel I5 is mounted on the upper drive shaft for stabilizing the rotation of the turntable. A record 20 is cut by the stylus of a cutter head IB mounted on an assembly IQ which, in turn, is moved radially across the record 2u by means of a lead screw 22. The lead screw 22 is mounted on a bracket 25, one end of which is rotatable upon a conical bearing 26, and the other end of which is rotatable in e. bearing 21.

The lead screw 22 isgeared to a vertical shaft 28 within a housing 36 of the bracket 25 (see Fig.`

2). The shaft 28 is enlarged at the lower end thereof to form a socket or thimble 32 to which is fastened, by screws 33, a flanged disc 34 having a resilient lpacl 38 suchvas rubber or felt on the underside thereof; The shaft 28 has mounted thereon a gear 38 rotatable in a' bearing member 35, the gear '38 meshing with a gear 40 on the lead screw 22.

The turntable 5 has a square-shanked spindle 'u either integral with the turntable or amxed thereto,4 and is shown in Fig. 2 inserted within 42. Between the member 42 and the interior of socket 32 is4 shown a rubber bushing 44, which bushing is firmly attached to both the innerwall Furthermore, should the surface'v of the 'turntable 5 not rotate in a single plane or'invaplane not parallel to the piane of the axis of lead screw 22, the resilience of the pad will not shift the axis of rotation of shaft 28.

In the above mechanism just described, it will be noted that, because ofthe flat-sided'spindle and its connecting element, there is a positivo angular relationship between the rotation of the' turntable 5 and the lead screw 22 which drives the cutter head. I8. This is a particularly'desirable feature. Furthermore. to aid in making the connection, the shank 4I has a square cross-section so'that connection may be made-in at least four different angular positions. The novel construction of the connecting unit, however, permade. Thus, greater tolerances are the manufacture of the apparatus.

It sometimes occurs in the commercial operation of the above-described Vapparatus that the turntable spindle 4I or turntable has considerable eccentricity, such that the coupling unit described above is insufficient to compensate therefor. The result is a binding action between the lead screw assembly and the spindle. 'Io prevent this binding action, a provision has been made to permit the entire lead screw assembly to be bodily translated along the axis of the lead screw by a special mounting of the assembly as shown in Figs. 4 and 5.

y In Fig. 4 is shown an enlarged housing portion 45 of the bracket 25 with a set screw tl therein for the adjustment of the conical bearing 25. The housing 45 is mounted to permit the vertical movement of the spindle and of the lead screw 22 by providing two conical bearings 49 carried by the ends ofa yoke 5D, the yoke having an axle 5I to permitrotation of the lead screw assembly. This end of the lead screw may be adjusted as to height by means of a set screw 53 passing through a bearing sleeve 54 and a sleeve 55 and contacting the axle 5I in a groove 56. The sleeve 54 has a circular flange 51, this flange resting upon a circular washer bearing 58 attached to the mounting board 8 by means of screws, one of which is shown at 60. The flange 51 is overlaid with a circular washer @I and slightly spaced from the upper surface of flange 51 by a shoulder portion 59 of the bearing 5B. The bearing 58 and washer 6I are affixed to one another by means of screws, one of which is shown at 62. The flange 51 is loosely held between the washer 6I and the bearing 58, while provision is made for a lateral movement of the axle 5I by making the outside diameter of the ange 51 smaller than the internal diameter of the shoulder., portion 59. To accommodate this Y movement, the internal diameter of the washer the broached aperture of a. cylindrical member 5I is larger than the external diameter of sleeve 54. By this interleaving oi the flange 51 and washers 58 and 6I, the sleeve 54, axle 5I and entire lead screw assembly may 'be translated horizontally in accordance with vthe lateral pressure on the assembly by bodily movement of the spindle 4 I. Thus, any binding action at the spindle is relieved, preventing variations in load on the motor.

From the above description, it will be observed that to avoid the deleterious effects of minor eccentricities or irregularities in the connection between the spindle 4I and the shaft 28, the couv pli-ngunit 32, ,42 and 441s provided. Should the irregularities or eccentricities be'too-large for this unit to accommodate, the mounting in Figs. 4 and 5 permits the entire lead screwassembly to be bodily moved' along the axis of the lead screw to prevent these discrepancies from interfering with recording'. Ifthe l spindle coupling unit is rather stiif, both the spindle unit and the assembly mounting may function simultaneously to mits any of these angular connections to be made without affecting the recording should any bindprovide a uniform motor load.

What I claim as my invention is:

1. In combination, a. lead screw adapted to be driven from a spindle having an axis at right angles to the axis of said lead screw, said spindle having eccentricities in the rotation thereof. means for positively connecting said spindle and said lead screw in a plurality of predetermined angular relationships,` said means including a shaft, a. gear thereon, and a gear on said lead screw meshing withy said shaft gear, means inprovided forl spindle having a square shank, means for connecting said screw to said spindle about said shank, said means including a gear on said lead screw meshing with a gear driven by said spindle, means for compensating for small irregularities of said shank, and means'included in said fixed mounting for compensating for larger irregularities of said spindle.

3. A combination in accordance with claim 2A in which said first-mentioned compensation means comprises a kmember having a square opening to accommodatesai'd shank and a re.

silient bushing surrounding said member for transmitting rotation of said member to said 4. A combination in accordance `with claim 2 in which said second-mentioned compensation means comprises a bearing rotatable and` slidable in a plane parallelv to the plane of said turntable.

5. A sound recording system comprising a turntable, means for rotating said turntable, a spindle at the center of said turntable, a lead screw one end of said lead screw being mounted adjacent the rim of said turntable, and the other end of said lead screw being adapted to be connected to said spindle in a plurality of predetermined angular relationships, means for connecting said spindle and said lead screw, said means spindle.

including a gear on said lead screw meshing with silient bushing attached to said cylinder intermediate said cylinder and said shaft.

7. A mechanism for a sound recording device comprising a turntable', a spindle on said turntable having a square shank adapted to be rotated with said turntable, a shaft adapted to be periodically positioned in coaxial alignment with said spindle and supported by said turntable, said shaft having an enlarged thimble portion, a'cylindrical member Within said thimble portion, said member having a square aperture adapted to accommodate said shank in a plurality of predetermined angular positions, and a resilient" member interposed between said member and the interiorv of said thimble to prevent small eccentricities in rotation of said spindle and turntable from being transmitted to saidshaft, and means at the other end of said shaft for preventing larger eccentricities in rotation of said spindle' and turntable from 'varying the load on said 8. A mechanism in accordance with claim 7 in which said resilient member is vulcanized to Athe members contacted thereby.

9. A lead screw mechanism for a sound recorder comprising a turntable, a'spindle for said turntable and adapted to be rotated therewith, said spindle and turntable being subject to-eccentricities in rotation, a horizontally disposed lead screw having one end translatable about a fixed mounting, a gear on said lead screw,v a vertically disposed shaft for rotating said screw, a gear on ,said shaft meshing with said lead screw gear,

means for resiliently connecting said spindle to said shaft in a plurality of predetermined angu, larpositions, said connecting means insulating said screw from small eccentricities in rotation of said spindle and turntable, and means for permitting longitudinal. translation of said llead screw along the rotational axis thereof to accommodate larger eccentricities -in rotation of said spindle and turntable.

10. A lead screw mechanism in accordancel with claim 9 in which said last-mentioned means includes an interleaved bearing having a clear-r` ance between the outer and inner diameters of leaves inthe same plane.

MILFORD E. COLLINS. 

